We can quantify the difference in the size of the two stars using Stephan's Law.
So the surface area of 
Ori is 
the surface
area of the Sun. This star has a radius 432 times larger than the Sun. It is
cool, yet huge hence the name 
.
Can play the same game with the low-luminosity hot stars at
the left side of the H-R Diagram. Despite the fact that they have
lots of energy radiated per unit surface area, they have a small
total energy radiated - they must have small surface areas and get
called 
.
You can play this game with all the stars and find an enourmous
range of sizes from around 1/100 R 
to nearly 1000 R